1. Field of the Invention
The present invention relates to a headphone device in which a loudspeaker unit is held within a housing, which in turn is supported by a supporting member, such as a hanger, at each end of a headband.
2. Description of the Prior Art
In a conventional headphone device adapted to be attached to a user's headband, by means of a resilient head a loudspeaker unit is contained within a housing which is supported at each end of the headband by a loudspeaker supporting member, such as a hanger.
The housing holding the loudspeaker unit is molded from synthetic resins, such as ABS or acrylic resins into a cup-shaped housing having substantially uniform wall thickness. The loudspeaker unit is positioned within the housing so that the sound radiating side of the loudspeaker unit, that is, the side fitted with the side of the loudspeaker unit is also contained within the housing. Upon driving the conventional headphone device, sound waves are radiated from user's auricle, and so that the magnetic circuit on the rear side of the unit will be accommodated within the housing.
In such headphone device having its loudspeaker unit accommodated within the housing, the sound wave radiated from the front surface of the loudspeaker unit towards the user's auricle, and sound waves are radiated from the rear side of the loudspeaker unit to the inside of the housing.
The loudspeaker unit is held within the housing so that the diaphragm is parallel to a smooth flat inner surface of the housing. When the sound waves, radiated from the rear side of the loudspeaker unit are reflected after impinging on the inner surface of the housing, a standing wave is generated. As a result, the sound reproducing properties are lowered and, hence, the reproduced sound heard by the user is also of inferior in quality.
Further, vibrations from the loudspeaker unit are transmitted to the housing which may cause the housing to resonate at a specific frequency. When the housing is constructed with a smooth flat inner surface and uniformed wall thickness, as previously described, the resonant oscillations are typically concentrated at one point. As a result, the sound pressure level at the resonant point is increased significantly thus deteriorating the acoustic properties of the reproduced sound heard by the user. Further, since the resonant oscillations are concentrated at one point of the housing, the housing itself is subjected to mechanical ringing thus, further to deteriorating the accoustic properties of the reproduced sound head by the user.